Dispensing adhesives onto surfaces without contacting the surface with the tip of the dispense nozzle is difficult because of the characteristics of the adhesives, in particular the low viscosity and the tendency for the adhesive to cure on/in the tip of the nozzle. One application where the application of an adhesive to a surface has been difficult is the case mouth of an ammunition round. Various methods and apparatus have been developed for applying sealant materials to the inside of the case mouth of cartridge cases. The sealant is used to help prevent moisture from getting inside the cartridge case and improves the performance of the bullet in outdoor environments, while also increasing the storage life. The types of sealant material used and the manner in which they are applied affect how the bullet is secured to the cartridge case. The bullet must be securely held in the case mouth of the cartridge case so that it does not fall out during manufacture or when being used and the seal must isolate the interior of the cartridge case from the exterior environment. Preferred sealants provide effective sealing properties and provide sufficient, but not excessive, adhesion between the bullet and the case mouth of the cartridge case.
In the past, the case mouths of cartridge cases have been sealed to prevent moisture infiltration around the bullet by applying a sealant to the inside of the case mouth before beginning other loading operations. Traditionally, the preferred sealant was a black asphaltic tar. It was applied wet and set aside for drying and curing. Once the sealant dried, the frictional heat from seating the bullet partially re-melted the tar, ensuring a good seal. However, this method was time consuming, did not allow high throughputs, and after application the sealant has a short work life, meaning projectiles had to be assembled with a pre-set time or they would not seal.
There is no proven method in the prior art for applying an anaerobic adhesive to an ammunition case mouth and primer. Various attempts have been made to use touch transfer dispensing methods to apply the sealant to the case mouth. However, touch transfer has not been found to be an optimal method for several reasons. First, when dispensing on the primer, the dispense must be carried out with the bullet in a horizontal position. This requires a mechanism that slides in and out as the bullet passes by on a conveyor and greatly reduces throughput potential. Second, anaerobic adhesives begin to cure when they contact metal. Thus, anaerobic adhesives used with a touch transfer method begin to cure when the dispense tip contacts the active metals (i.e., brass and copper) of the bullet. This reduces throughput and current touch transfer methods typically produce no more than 200 rounds per minute. Accordingly, there is a need for a dispense system with increased throughput, wherein the adhesive does not contact the bullet when the adhesive is in the dispenser.